Porta Metronia

The Porta Metronia was one of the Aurelian Walls, built in 270 in Rome, Italy.

History
Built in conjunction with the Aurelian Walls, the Porta Metronia was seated at the end of the Middle Ages, allowing Pope Callixtus II to create a small channel through it for the Acqua Mariana, a river whose stagnant waters would later cause an outbreak in 1601.